What is Gene Expression ?

Gene expression is the process by which a gene is activated to produce a certain protein. Cells are able to respond to changes in the environment in two ways: 1.) by controlling the production of enzyme molecules that cause expression of a gene; and 2.) by controlling the activities of enzymes that are already present through the use of feedback mechanisms.

The control mechanism for gene expression is very different in prokaryotic cells than in eukaryotes.
The way in which a specific gene expresses itself is of particular interest to scientists. Many diseases have been found to be genetically-based. Therefore, the ability to control the form and behavior of a cell or an organism would prove especially useful in the prevention and cure of disease.

One area that holds real promise in the near future is in the cloning of new tissues or organs to replace those that have become injured or diseased. Cells from the body can be used to produce clones because each cell contains a full complement of DNA. Cloning involves removal of a cell from an organism, and then providing that cell with all of the nutrients, gases, and physical conditions necessary for its growth, development, and reproduction.

The larger question is: since each and every cell has the same DNA information, what are the determining factors that cause a newly formed skin cell to form the specialized structures that enable it to perform the functions of skin, rather than, say, the types of protein structures that characterize muscle cells?